This invention relates to electrodes for use in electrocatalytic processes. More particularly, the invention relates to electrodes containing metal in a dispersed form, and to methods for the preparation and use of such electrodes.
It is known that electrodes having high catalytic activity in electrocatalytic reactions can be prepared by depositing a film of a polymer on a conductive base member (the term "conductive" and other terms of similar import are used herein to refer solely to electrical properties) and incorporating organometallic compounds into the polymer films; see:
Doblhofer et al., J. Electrochem. Soc., 127, 1041(1970); PA1 Doblhofer et al., Ber. Bunsenges, Phys. Chem., 82, 403(1978); PA1 Ikada et al., J. Am. Chem. Soc., 104, 2683(1982); and PA1 Bettlheim et al., J. Electroanal. Chem. 110, 93(1980). PA1 Kiwi Stabilization of Platinum Particles by Polymers in Aqueous Solutions, pp. 246 et seq, in Tadros (ed.), The Effect of Polymers on Dispersion Properties, Academic Press, London (1980). PA1 Bookbinder et al., Proc. Natl. Acad. Sci. USA, 77, 6280(1980); PA1 Bookbinder et al., J. Am. Chem. Soc., 103, 7656(1981); PA1 Bruce et al., J. Phys. Chem., 86, 1552(1982); and PA1 Dominey et al., J. Am. Chem. Soc., 104, 467(1982).
It is also known to spray microcrystalline particles of platinum on the outer surface of a polymer layer covering an electrode; see:
Attempts have been made to produce somewhat similar electrodes having elemental metal dispersed in the polymer form. For example, elemental platinum has been incorporated into a polymer film of [N,N'-bis(3-(trimethoxysilyl)propyl-4,4'-bipyridinium] dibromine covalently attached to a p-type silicon photocathode surface, to produce an electrode useful for photoelectrochemical hydrogen reduction; see:
Although the first and third of these papers report electrochemical and other studies suggesting that the elemental platinum is present as discrete particles, scanning electron microscopy studies reported in the same paper fail to show the presence of discrete particles of the metal in the polymer film. Accordingly, it appears that the electrodes thus prepared contain the metal in the form of separate atoms or very small assemblies of atoms rather than observable discrete particles in the polymer film. Preparing such electrodes having the metal in the form of discrete particles within the polymer film would be desirable in order that a large surface area of metal may be available for catalytic purposes and because such dispersed metal particles would be expected to have better catalytic properties than the prior art electrodes discussed above.
It has now been found that it is possible to prepare electrodes having discrete particles of metals or metal oxides dispersed within a polymer layer and that such electrodes have highly desirable electrocatalytic properties.